U.S. patent number 8,783,939 [Application Number 13/383,701] was granted by the patent office on 2014-07-22 for extruder.
This patent grant is currently assigned to Blach Verwaltungs GmbH & Co. KG. The grantee listed for this patent is Josef A. Blach. Invention is credited to Josef A. Blach.
United States Patent |
8,783,939 |
Blach |
July 22, 2014 |
Extruder
Abstract
An extruder is provided that has a housing with at least two
axially parallel shafts which are capable of being driven in the
same direction and with at least two-flight intermeshing conveying
elements stripping each other at an axial distance (Ax) with a
small clearance over the entire circumference. The extruder has a
distance between the comb of the at least one further flight and
the inner wall of the housing. Each conveying element has at least
two conveying sections rotated through an angle, wherein each
conveying section has an axial length corresponding to at most the
outer diameter of the conveying element.
Inventors: |
Blach; Josef A. (Ehrwald,
AT) |
Applicant: |
Name |
City |
State |
Country |
Type |
Blach; Josef A. |
Ehrwald |
N/A |
AT |
|
|
Assignee: |
Blach Verwaltungs GmbH & Co.
KG (Lauffen, DE)
|
Family
ID: |
42199465 |
Appl.
No.: |
13/383,701 |
Filed: |
July 16, 2009 |
PCT
Filed: |
July 16, 2009 |
PCT No.: |
PCT/EP2009/005162 |
371(c)(1),(2),(4) Date: |
April 10, 2012 |
PCT
Pub. No.: |
WO2011/006516 |
PCT
Pub. Date: |
January 20, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120188840 A1 |
Jul 26, 2012 |
|
Current U.S.
Class: |
366/85 |
Current CPC
Class: |
B29B
7/489 (20130101); B29C 48/405 (20190201); B29C
48/54 (20190201); B29B 7/483 (20130101); B29C
48/64 (20190201); B29C 48/65 (20190201); B29C
48/2715 (20190201); B29C 48/402 (20190201); B29C
48/507 (20190201); B29C 48/425 (20190201); B29B
7/485 (20130101); B29C 48/57 (20190201); B29C
48/395 (20190201); B29C 48/2517 (20190201); B30B
11/243 (20130101); B29C 48/435 (20190201); B29C
48/2564 (20190201); B29C 48/03 (20190201); B29C
48/43 (20190201) |
Current International
Class: |
B01F
7/24 (20060101) |
Field of
Search: |
;366/74.6,85,76.6,79,76.4,82,83,84 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2728438 |
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Dec 2009 |
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CA |
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862668 |
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Jan 1953 |
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DE |
|
3123699 |
|
Apr 1982 |
|
DE |
|
10207145 |
|
Sep 2003 |
|
DE |
|
10233213 |
|
Feb 2004 |
|
DE |
|
102004010553 |
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Sep 2005 |
|
DE |
|
102008016862 |
|
Oct 2009 |
|
DE |
|
102008029305 |
|
Dec 2009 |
|
DE |
|
0002131 |
|
Nov 1978 |
|
EP |
|
0788867 |
|
Aug 1997 |
|
EP |
|
0788868 |
|
Aug 1997 |
|
EP |
|
2009152910 |
|
Dec 2009 |
|
WO |
|
Other References
International Search Report dated Aug. 26, 2010 corresponding to
International Patent Application No. PCT/EP09/05162. cited by
applicant .
International Search Report and Written Opinion for
PCT/EP2011/001477 dated Aug. 12, 2011. cited by applicant.
|
Primary Examiner: Soohoo; Tony G
Assistant Examiner: Bhatia; Anshu
Attorney, Agent or Firm: Thompson Coburn LLP
Claims
The invention claimed is:
1. An extruder comprising: a housing having an inner wall, and at
least two axially parallel shafts, the shafts being driven in a
common direction and provided with at least two flight conveying
elements, the at least two flight conveying elements intermeshing
in a cross-section perpendicular to the shafts so as to strip each
other at an axial distance (Ax) with a small clearance over an
entire circumference, the at least two axially parallel shafts
being in the housing at a distance (a) between a comb of at least
one further flight and the inner wall of the housing, and wherein
each conveying element has at least two conveying sections rotated
through an angle, wherein each conveying section has an axial
length (Ls) corresponding to at most 1/2 times an outer diameter
(Da) of the conveying element; wherein the distance (a) is greater
than a clearance distance (a') of a flight stripping the inner wall
of the housing; wherein the flight stripping the inner wall of the
housing has a flight depth (b) that is greater than a flight depth
(c) associated with the at least one further flight; and wherein
one conveying section is offset relative to the next conveying
section by an angle of no greater than 360.degree. /number of
flights.
2. The extruder according to claim 1, wherein the distance (a)
between the comb and the inner wall corresponds to at most half a
flight depth (b) of a first flight.
3. The extruder according to claim 1, wherein the angle of offset
from one conveying section to the next one is in steps.
4. The extruder according to claim 1, wherein, between two
conveying sections , a concentric annular section is provided
having a free passage height (H) to the inner wall of the housing
which is equal to or larger than half the flight depth (b).
5. The extruder according to claim 1, wherein the distance (a) of
the further comb from the inner wall of the housing vary within one
conveying element.
6. The extruder according to claim 1, wherein the flight depth (b)
of the at least two conveying sections varies.
7. The extruder according to claim 1, wherein the axial length (Ls)
of the conveying elements corresponds to a maximum of four times
the outer diameter (Da) of the conveying elements.
8. The extruder according to claim 1, wherein the at least two
axially parallel shafts comprises at least six axially parallel
shafts arranged along a circle at a common central angle.
9. The extruder according to claim 1, wherein the flight depth (b)
of at least one flight of the at least one conveying element is
smaller than the flight depth of the remaining conveying elements
exclusively comprising flights with combs which are substantially
in close contact with the inner wall of the housing.
10. The extruder according to claim 1, further comprising a ratio
of the outer diameter (Da) of the conveying elements to an inner
diameter (Di) of the conveying elements ranges from 1.25 to
2.3.
11. The extruder according to claim 10, wherein the ratio has a
maximum in a filling zone of the extruder.
12. The extruder according to claim 1, wherein the intermeshing
conveying elements are formed by screw sections offset at an angle
as conveying sections.
13. The extruder according to claim 12, wherein the screw sections
are offset at an angle such that the comb of each flight of the
conveying element is formed by adjoining alternating comb sections
substantially stripping the inner wall of the housing closely as
well as comb sections having the distance (a) from the inner
wall.
14. The extruder according to claim 1, wherein the intermeshing
conveying elements are formed by kneading blocks, with the
conveying elements offset at an angle forming cam disks of the
kneading blocks.
15. The extruder according to claim 14, wherein each cam disk
consists of at least two dividing plates, wherein the comb of the
one dividing plate substantially strips the inner wall closely,
whereas the adjacent comb of the adjacent dividing plate has the
distance (a) from the inner wall.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a U.S. National Stage Entry under 35 U.S.C.
.sctn.371 of International Application No. PCT/EP2009/005162 filed
on Jul. 16, 2009, the contents of which are incorporated by
reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a twin-shaft or multi-shaft extruder.
2. Description of Related Art
Twin-shaft or multi-shaft extruders having shafts which are capable
of being driven in the same direction substantially comprise
closely intermeshing shaft conveyors as well as kneading blocks as
conveying elements. For the purpose of easy adaption of geometry
and material to the different process tasks, appropriate components
in the required variety are usually formed in such a way that they
are pluggable onto the supporting shaft so as to rotate
therewith.
In order to align the required flexibility with the high demands on
efficiency and safety, geometric limitations are indispensable,
such as only one or few element lengths and/or the same mounting
position at the ends, whereby the necessary screw pitches, element
types and/or overall lengths are substantially restricted. In order
to achieve the required adaptability of the elements, only the end
positions and/or lengths have to be observed so that the geometric
conditions in between, such as the pitch and the offset angle,
continuous or in steps, can freely be selected from a procedural
point of view. In the product throughput, effectiveness and the
kind of energy transfer from the conveyor structures to the product
affect both the temperature and quality of the product. In order to
wet solids in powder form with viscous material and disperse and/or
disaggregate them therein, shear flows or, better still,
elongational flows have to be generated in the highly viscous
material.
EP 0 002 131 B1 discloses a self-cleaning type extruder including
two shafts and a two-flight screw profile in which one comb of the
screw has a small distance and the second one a great distance from
the inner wall of the housing.
As a result, two flights separated by a comb at a great distance
from the wall of the housing are formed between two adjacent combs
at a small distance from the inner wall of the housing. Thus, the
product may freely flow from one flight into the other one, whereby
it flows into the first flight until the latter is filled, whereas
the second flight is filled partly at most. Hence, the product is
subjected to the necessary homogenous treatment only in the first
flight so that the product is treated unequally, since the exchange
of material from the first flight to the second flight is
insignificant.
However, the homogenization and dispersion of the solids in a
viscous matrix, which can be achieved by means of the known
extruders, is still unsatisfactory. This particularly applies to
solids with a particle size in the micrometer (.mu.m) range.
BRIEF SUMMARY OF THE INVENTION
It is the object of the invention to provide an unrestrictedly
self-cleaning multi-shaft extruder by which it is possible to
improve the product quality significantly and effectively.
According to the invention, at least two-flight conveying elements
are used, consisting of circular arcs in profile section, i.e. the
cross-section perpendicular to the shaft, with intermeshing
conveying elements substantially stripping each other closely over
the entire circumference. In addition to two-flight conveying
elements, three-flight conveying elements are particularly
used.
In this case, the comb of the first flight strips the inner wall of
the housing at a small clearance, whereas there is a greater
distance between the comb of the at least one further flight and
the inner wall of the housing. Each conveying element has at least
two conveying sections offset to each other continuously or in
steps, with each conveying section preferably having an axial
length corresponding to at most the total, preferably at most half
the outer diameter of the conveying element, hence the total and/or
half the inner diameter of the inner wall of the housing. The axial
length of the conveying sections of the intermeshing conveying
elements is preferably equal, but it can also vary.
Thus, each conveying section has a correspondingly large flight
depth at an angle of 90.degree. in case of two flights, and a
correspondingly small flight depth at an angle of 60.degree. in
case of three flights. That is to say in the conveying element
according to the invention, a first comb at a small clearance from
the inner wall of the housing is followed by a second comb at a
greater distance from the inner wall of the housing, and at an
angle thereto, a correspondingly large flight depth as well as a
small flight depth at a maximum distance of 1 Da or 1/2 Da
(Da=outer diameter of the conveying element or inner diameter of
the inner wall of the housing).
This means that an extensive exchange of material is possible
across all feed channels in the circumferential direction from
channel to channel involving multiplied flow divisions, with the
material exchange being carried out radially as well as axially in
the same way with different and varying flight depths and
corresponding comb/housing clearances. Thus, the filling degree is
equal in all channels. Due to the permanent geometric chicane in
the alternation of comb and flight in rapid succession in the
circumferential and axial direction, a particularly high density of
elongational flows is produced. Since this takes place without the
undesirable decrease of viscosity in all feed channels in the
entire cross-section and over the entire length of the conveying
element, a more effective and more rapid mixing is achieved and a
significantly higher product quality with a more uniform
homogenization. This is substantially attributed to two sharp
deflections at the transition of the product from one supporting
shaft to the next one in case of the twin-shaft extruder, and, in
particular, 12 deflections in a six-shaft extruder as well as 24
deflections in a twelve-shaft extruder, which cause a further
intensification of the effective forces in the product.
By means of viscosity of the continuous phase, tensile and bending
forces are thus repeatedly exerted on the fatigue strength of the
agglomerates of solids, which results in the fatigue fracture of
the latter. According to the invention, an effective homogenization
and dispersion of the solid is achieved, that is to say even in
case of solid particles having a particle size in the .mu.m range,
hence less than 100 .mu.m, in particular less than 10 .mu.m.
By means of the conveying element according to the invention, the
product is thus subjected to constantly varying flight depths and
material velocities and hence elongation processes over a very
short length.
According to the invention, an extensive exchange of material is
achieved as a result of the great distance of the one comb from the
inner wall of the housing, whereas at the comb stripping on the
inner wall, only a minor exchange of material takes place, but the
greatest dispersing effect is achieved due to maximum strain. Since
according to the invention, said comb consists of short sections,
the product is subjected to extreme strain only in small areas,
however, which is why the temperature of the product may be kept
altogether low with the consequence that even in the extremely
strained areas, the product cannot be damaged and is thus treated
altogether gently.
Therefore, the extruder according to the invention is also suited
for the processing of sensitive products, for example the
reprocessing of polyethylene terephthalate (PET).
Preferably, the conveying element according to the invention is
formed in one piece, for example by milling of a corresponding
piece of metal. Whereas according to the invention, the comb of the
first flight substantially strips the inner wall of the housing
closely, thus has only a small clearance of, for example, less than
1 millimeter (mm), preferably less than 0.5 mm, with an outer
diameter Da of the conveying element of less than 100 mm, the
distance of the comb of the at least one further flight of the
screw element from the inner wall of the housing preferably
corresponds to at most half the flight depth of the first flight,
preferably, however, more than 1 mm.
Preferably, the pitch of the combs of the conveying elements ranges
from 1/3 Da to infinite. That is to say the conveying element
according to the invention can, for example, also be formed as a
kneading block.
The flight pitch of the conveying element can differ from conveying
section to conveying section. In addition, the ratio of the outer
diameter Da to the inner or core diameter Di may vary from
conveying section to conveying section.
Preferably, the axial length of the conveying element is at least 1
Da and should not exceed 4 Da, because in case of a length of more
than 4 Da, it is difficult to handle, for example difficult to
detach from the shaft.
The extruder according to the invention has at least two,
preferably at least three, axially parallel shafts which are
capable of being driven in the same direction. The shafts may be
arranged on a straight, plane surface. Instead, shafts arranged
along a circle or a circular arc can also be provided in the cavity
of the housing of the extruder, wherein both on the radially
internal and external side of the cavity, the housing of the
extruder is equipped with concave circular segments parallel to the
extruder axis, in which the screw elements are substantially guided
closely, as described in EP-B-0788867, for example.
In this case, at least six shafts are preferably arranged at the
same central angle distance along a circle.
By means of the conveying elements according to the invention, the
material can thus pass through the shaft rim from one side of the
cavity to the other side. In case of six shafts arranged at the
same central angle distance along a circle, for example, the
homogenization is substantially increased by twelve deflections of
the product.
The flight depth of the first comb of the conveying element
according to the invention may be smaller than the flight depth of
the remaining standard conveying elements of the extruder, that is
to say the conveying elements the combs of which are substantially
in close contact with the inner wall of the housing. Thus, the
conveying element in the material filling zone of the extruder may,
for example, have a particularly large flight depth. The ratio of
the outer diameter Da of the conveying elements to the inner
diameter Di, for example, may range from 1.25 to 1.85. Preferably,
the ratio of the outer diameter of the conveying element to the
inner diameter has its maximum in the filling zone of the
extruder.
The shaft and the at least one conveying element according to the
invention, which supports the shaft, preferably form a single
component. Due to the fact that the shaft and the conveying element
are formed in one piece, a significantly higher torque can be
transmitted. For example, the shaft, including the driving shaft,
as well as the conveying element in the area of the filling zone,
including the fusing zone, may consist of a single component.
The filling zone can be followed by a zone with a conveying element
having a smaller ratio of the outer diameter to the inner diameter,
which, in turn, can be followed by a conveying element having a
larger ratio of the outer diameter to the inner diameter etc.
Between two conveying sections of the conveying element, a
concentric annular section may be provided, which on the
circumference, has a short axial length of at most 1/5 of the axial
length of one conveying section and/or the shortest conveying
section in case of conveying sections of different length, and
which has a free passage height to the inner wall of the housing
being equal to or larger than half the pitch depth.
The annular section may be circular, but it may also deviate from
the circular shape. Due to the annular section between two
conveying sections of the conveying element, the conveying speed is
reduced in the axial direction and hence the dispersing effect is
increased.
The conveying sections of the intermeshing conveying elements of
the extruder according to the invention may consist of screw
sections.
Preferably, the screw sections are offset at an angle such that the
comb of each flight of the conveying element is formed by adjoining
alternating comb sections substantially stripping the inner wall of
the housing closely as well as comb sections having a distance from
the inner wall of the housing.
That is to say the conveying element is a screw element, wherein
each comb of the screw element alternately consists of a comb
section stripping on the wall of the housing and a comb section
having a great distance from the wall of the housing.
In screw sections, the comb stripping on the inner wall of the
housing, i.e. having a small distance from the inner wall of the
housing, has a small width, and the comb being arranged at a
distance from the inner wall of the housing has a large width.
Accordingly, in a conveying element the screw sections of which are
offset at an angle such that the comb of each flight of the
conveying element is formed by adjoining comb sections
substantially stripping the inner wall of the housing closely in
alternating sequence and/or having a distance from the inner wall
of the housing, narrow and wide combs alternate along the comb of
each flight.
Instead of being formed as screw sections, however, the conveying
sections of the conveying element of the extruder according to the
invention can also be formed in any other way. Thus, the
intermeshing conveying elements may especially be formed by
kneading blocks, that is to say the conveying sections can be
formed by the cam disks of the kneading blocks offset at an
angle.
Such kneading blocks are used for mixing and kneading the product.
Due to the cam disks offset at an angle, however, they also have a
conveying effect.
The cam disks have a cross-section which is perpendicular to the
shafts and corresponds to the cross-section through a screw element
and/or a screw section.
This means that like the screw section, each cam disk also has a
comb substantially stripping the inner wall of the housing closely
and at least one further comb at a distance from the inner wall of
the housing.
The combs of the cam disks of the kneading block stripping closely
on the inner wall of the housing form the first flight, and the
combs of the cam disk of the kneading block arranged at a distance
from the inner wall of the housing form the at least one further
flight. Preferably, the kneading blocks are likewise formed in one
piece, for example by milling of a piece of metal.
As described above, annular sections can also be provided between
two cam disks of the kneading block in order to reduce the flow of
material in the axial direction and thus increase the dispersing
effect.
According to the invention, the intermeshing conveying elements
strip each other at a small clearance over the entire
circumference. At the same time, the comb of the first flight
closely strips the inner wall of the housing. In addition, the comb
of the first flight strips the core and the flanks of the
corresponding conveying element. That is to say said comb of the
respective conveying section closely strips the core and the flanks
of the corresponding conveying section with which it intermeshes.
This applies to screw elements as conveying elements as well as
kneading blocks as conveying elements. If kneading blocks comprise
said concentric annular sections, however, they carry out the
stripping of the flanks.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is exemplified in more detail below based on the
enclosed drawings, in which:
FIG. 1a shows a cross-section through a first conveying section and
FIG. 1b a second conveying section of a conveying element rotated
through 180.degree. in relation to FIG. 1a;
FIGS. 2, 3 and 4 show a perspective view and/or a lateral view
and/or a longitudinal section of two intermeshing conveying
elements;
FIGS. 5a to 5f each show a section along the lines A-A, B-B, C-C,
D-D, E-E and F-F according to FIG. 3;
FIG. 6 shows a lateral view of two intermeshing conveying elements
of a twin-shaft extruder;
FIGS. 7 and 8 show a lateral view and/or a section of two
intermeshing conveying elements of a twin-shaft extruder having
annular sections;
FIGS. 9 and 10 show a lateral view and/or a section of a
multiple-shaft extruder having shafts arranged along a circle;
FIG. 11 shows a perspective view of two intermeshing conveying
elements of a variant of the conveying element according to FIGS. 2
to 4;
FIGS. 12 to 14 show a perspective view and/or a front view and/or a
lateral view of two intermeshing kneading blocks; and
FIGS. 15 to 17 show a perspective view and/or a front view and/or a
lateral view of a variant of the kneading blocks according to FIGS.
12 to 14.
DETAILED DESCRIPTION OF THE INVENTION
According to FIGS. 1a and 1b, the housing of the extruder has a
cylindrical inner wall 1. A two-flight conveying element 2 is used,
which according to FIGS. 1a and 1b, consists of two conveying
sections 3 and 4, namely the first conveying sections 3 and the
second further conveying sections 4 rotated through 180.degree. in
relation to the first conveying sections 3.
The profile section, i.e. the cross-section perpendicular to the
shaft of the conveying sections 3, 4 consists of circular arcs. The
circular arc A-B in Figure la and/or the circular arc A'-B' in FIG.
1b represent the comb 5, 5' of the first flight, which is
substantially in close contact with the inner wall 1 of the
housing, that is to say at a small clearance a', whereas the
circular arc C-D and/or C'-D' represents the comb 6, 6' of the
second flight, which is arranged at a distance a from the inner
wall 1. According to FIG. 1a, the flight with the comb 5 has a
large flight depth b and the second flight with the comb 6 has a
small flight depth c. The long circular arcs A-C and B-D and/or
A'-C' and B'-D' each consist of three circular arcs, namely in the
centre of a circular arc with a diameter which corresponds to the
core diameter Di being followed on both sides by a circular arc
with a diameter the radius of which corresponds to the axial
distance Ax of the two conveying elements.
The second conveying section 4 according to FIG. 1b, which axially
follows the conveying section 3, can be formed by reflection of the
first conveying section 3 about an axis 7 or the axis 8 rotated
through 90.degree. in relation thereto, or may be achieved by
rotation through 180.degree..
The axis 7 is formed by the plane intersecting the shaft axis 10
and the centre of the comb 5; the axis 8 is formed by the plane
centrally intersecting the circular arcs AB and BC and the shaft
axis 10.
The outer diameter Da of the conveying element 2 may, for example,
be 10 to 50 mm, the inner diameter Di, for example, 7 to 30 mm, the
distance a, for example, 1 to 3 mm. The comb 5 may include an angle
.alpha. ranging, for example, from 15.degree. to 25.degree..
That is to say the second comb 6' of the second conveying section 4
being formed by the circular arc C'-D' and having the distance a
from the inner wall 1 of the housing is offset by 180.degree. in
relation to the second comb 6 of the first conveying section 3,
ditto the large flight depth b and the small flight depth c.
As exemplified by the conveying elements 31, 32 in FIG. 8, the
intermeshing conveying elements have an axial distance Ax and strip
each other over the entire circumference (FIGS. 5a, 8, 9, 13 and
16).
As can particularly be seen from FIGS. 1a, 1b and 3, the comb 5' of
the first flight of the one conveying element 12 substantially
strips the inner wall 1 of the housing as well as the flank 15 and
the core 16 of the conveying element 11 intermeshing therewith
closely.
According to FIG. 2, the one-piece conveying elements 11, 12 of a
twin-shaft extruder are provided with internal teeth 13, 14 in
order to plug them onto two axially parallel shafts rotating in the
same direction (not illustrated) so as to rotate therewith.
Each conveying element 11, 12 has an axial length Le of, for
example, 2.5 Da, preferably at most 4 Da, and consists of six
conveying sections 11a to 11f and 12a to 12f. The conveying
sections 11a to 11f and 12a to 12f of each conveying element 11
and/or 12 are arranged progressively in steps and are offset in
relation to each other by the same angle, for example 36.degree..
Each conveying section 11a to 11f and 12a to 12f has two flights.
Intermeshing conveying sections 11a to 11f and 12a to 12f are
substantially in close contact at a point C, that is to say at a
small clearance of, for example, less than 1 mm, as shown in FIGS.
5a to 5f.
As exemplified by the conveying elements 111 and 121, the comb 5
and/or 5' of the first flight of each conveying section according
to FIG. 1a is formed such that it is in contact with the inner wall
1 of the housing, whereas there is a greater distance a between the
comb 6, 6' and the inner wall 1 of the housing. The axial lengths
Ls of the conveying sections 11a to 11f and 12a to 12f each
correspond to approximately 1/3 of the diameter Da of the conveying
element 11, 12 and/or the diameter of the inner wall 1 of the
housing (FIGS. 1a and 1b). Due to the constantly varying flight
depth in accordance with the combs 5, 6 and 5', 6', the product is
subjected to continuous tensile stress. As illustrated by the
arrows 15 in FIG. 5b, there is also a sharp deflection of the
product in the area of the stripping points C.
In case of the twin screw according to FIG. 6, the conveying
elements 21, 22 comprise the conveying sections 21a to 21e and/or
22a to 22e, which are rotated through 180.degree. in relation to
each other, that is to say offset an angle of 180.degree..
According to FIGS. 7 and 8, the conveying elements 31, 32 comprise
conveying sections 31a to 31d and/or 32a to 32d, each having a
concentric annular section 33a to 33d and/or 34a to 34d. The
conveying sections 31a to 31d and 32a to 32d are rotated through
180.degree.. The dimension H of the annular gap 35, 35' between the
rings 33a and/or 34a and the inner wall 1 of the housing ranges
from 1/4 to 3/4 of the flight depth (b) and is, for example, half
the flight depth (FIG. 8).
On the circumference, the axial length La of the rings 33a to 33d,
34a to 34d is not more than 1/5 of the length Ls of the conveying
sections 31a to 31d, 32a to 32d. The rings 33a to 33d and 34a to
34d do not have to be exactly centric or circular. It is rather
sufficient if they substantially form centric circular
sections.
In case of the extruder according to FIGS. 9 and 10, the conveying
elements 41, 42, 43 . . . are mounted on axially parallel shafts
being arranged along a circle so as to rotate therewith, with the
conveying elements 41, 42, 43 . . . stripping each other over the
entire circumference. The conveying elements 41, 42, 43 consist of
conveying sections 41a to 41e having a profile offset by
180.degree..
As in FIGS. 2 to 5, the two conveying elements 11 and 12 according
to FIG. 11 also consist of conveying elements 11a to 11f and 12a to
12f, which are formed by screw sections.
According to FIG. 11, the screw sections 11a to 11f of the
conveying element 11 and the screw sections 12a to 12f of the
conveying element 12 are offset at an angle such that the comb 5',
6 of each flight of the conveying elements 11 and 12 is formed by
adjoining comb sections 5' substantially stripping the inner wall 1
of the housing closely, and comb sections 6 being arranged at a
distance (a) from the wall of the housing (FIGS. 1a and 1b), with
the comb sections 5' and the comb sections 6 alternating.
Thus, the conveying elements 11 and 12 according to FIG. 11 each
form screw elements.
As can be seen inter alia from FIG. 11, the comb 5, 5' in the screw
elements 11 and 12 substantially stripping on the inner wall of the
housing closely is narrower than the comb 6, 6' so that narrow
sections 5' alternate with wide sections 6.
Whereas FIGS. 2 to 7 and 9 to 11 relate to screw elements as
conveying elements and/or conveying elements with screw sections of
finite pitch, conveying elements with screw sections of infinite
pitch as conveying elements of intermeshing kneading blocks 50, 51
and/or 52, 53 are provided according to FIGS. 12 to 14 and FIGS. 15
to 17 in order to achieve a high degree of specific energy
input.
In this case, the kneading blocks 50, 51 according to FIGS. 12 to
14 consist of cam disks 50a to 50e and 51 to 51e offset at an
angle.
The cam disks 50a to 50e, 51a to 51e have a cross-section which is
perpendicular to the shafts and which corresponds to the
cross-section through the conveying element 2 according to FIGS. 1a
and 1b.
That is to say according to FIGS. 1a and 1b, each cam disk 50a to
50e and 51a to 51e has a narrow comb 5, 5' substantially stripping
the inner wall 1 of the housing closely and a further wide comb 6,
6' at a distance from the inner wall of the housing.
In this case, flights having a conveying effect are likewise
formed, as illustrated by the flight 58 in FIG. 12 (dashed line).
The flights of each kneading block 50, 51 are formed by alternating
wide combs 6, 6' and narrow combs 5, 5', as shown by the flight 58
according to FIG. 12.
According to FIG. 7, annular sections 50g to 50j and/or 51g to 51j
concentric to the shafts are provided between the conveying
sections or cam shafts 50a to 50f and 51a to 51f also in the
kneading blocks in accordance with FIGS. 12 to 14.
Since the gap between the wide comb 6 and the inner wall 1 of the
housing enables an extensive exchange of material, whereas there is
only a small clearance between the comb 5, the cam disks 51a and
the cam disk 50a, that is to say on the one hand, the product is
highly strained, but on the other hand, it is intensively
dispersed. As the strain only occurs in this small area, an
altogether gentle treatment of the product is achieved.
According to FIGS. 15 to 17, each cam disk 52a to 52e and 53a to
53e of the intermeshing kneading blocks 52, 53 consists of two
dividing plates, as illustrated by the dividing plates 54, 55 of
the cam disk 53a.
The kneading blocks 52, 53 according to FIGS. 15 to 17 each consist
of five twin disks 52a to 52e and/or 53a to 53e. As a result, there
are altogether ten dividing plates 52, which are identified by the
numerals (1) to (10) as regards the kneading block 52 in FIG. 17.
The odd-numbered dividing plates (1), (3), (5), (7), (9) are
rotated through 180.degree. in relation to the even-numbered
dividing plates (2), (4), (6), (8), (10), and the even-numbered
dividing plates are rotated through 225.degree. (180.degree. plus
45.degree.) in relation to the odd-numbered dividing plates.
As shown by the dividing plates 54, 55, the comb 56 of the one
dividing plate 54 substantially strips on the inner wall of the
housing closely, whereas the adjacent comb 55 of the adjacent
dividing plate 55 of the cam disk 53a has a distance from the inner
wall 1 of the housing corresponding to the distance a according to
FIGS. 1a and 1b.
* * * * *